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.\"     @(#)psignal.3	8.2 (Berkeley) 2/27/95
.\" $FreeBSD: src/lib/libc/gen/psignal.3,v 1.17 2007/01/09 00:27:54 imp Exp $
.\"
.Dd February 27, 1995
.Dt PSIGNAL 3
.Os
.Sh NAME
.Nm psignal ,
.Nm strsignal ,
.Nm strsignal_r ,
.Nm sys_siglist ,
.Nm sys_signame
.Nd system signal messages
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In signal.h
.Ft void
.Fn psignal "unsigned sig" "const char *s"
.Vt extern const char * const sys_siglist[] ;
.Vt extern const char * const sys_signame[] ;
.In string.h
.Ft "char *"
.Fn strsignal "int sig"
.Ft "int"
.Fo strsignal_r
.Fa "int sig"
.Fa "char *strsignalbuf"
.Fa "size_t buflen"
.Fc
.Sh DESCRIPTION
The
.Fn psignal ,
.Fn strsignal ,
and
.Fn strsignal_r
functions locate the descriptive message
string for a signal number.
.Pp
The
.Fn strsignal
function accepts a signal number argument
.Fa sig
and returns a pointer to the corresponding message string.
.Pp
The
.Fn strsignal_r
function renders the same result into
.Fa strsignalbuf
for a maximum of
.Fa buflen
characters and returns 0 upon success.
.Pp
The
.Fn psignal
function accepts a signal number argument
.Fa sig
and writes it to the standard error.
If the argument
.Fa s
is
.Pf non- Dv NULL
and does not point to the null character,
.Fa s
is written to the standard error file descriptor
prior to the message string,
immediately followed by a colon and a space.
If the signal number is not recognized
.Pq Xr sigaction 2 ,
the string
.Dq "Unknown signal
is produced.
.Pp
The message strings can be accessed directly
through the external array
.Va sys_siglist ,
indexed by recognized signal numbers.
The external array
.Va sys_signame
is used similarly and
contains short, lower-case abbreviations for signals
which are useful for recognizing signal names
in user input.
The defined variable
.Dv NSIG
contains a count of the strings in
.Va sys_siglist
and
.Va sys_signame .
.Sh RETURN VALUES
.Fn strsignal
a pointer to the desired message or a NULL value indicating an error.  This
string is not to be freed by the caller.  Beginning with Mac OSX 10.7, this
string is unique to each thread.
.Pp
.Fn strsignal_r
0 if the message string is successfully copied in its entirety to
.Fa strsignalbuf .
.Pp
.Sh ERRORS
.Fn strsignal
will fail and no additional memory will be allocated if
one of the following are true:
.Bl -tag -width Er
.It Bq Er ENOMEM
There was insufficient memory to allocate storage space for the return value in the running thread.
.El
.Pp
.Fn strsignal_r
will return an error (but not fail) if one or more condition is met:
.Bl -tag -width Er
.It Bq Er ERANGE
.Fa buflen
is not long enough to fit the length of the message.
.Fa strsignalbuf 
will contain the message string that has been truncated and
NUL terminated to fit the length specified by
.Fa buflen .
.El
.Bl -tag -width Er
.It Bq Er EINVAL
.Fa sig
<= 0 or >= NSIG.
.El
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr perror 3 ,
.Xr strerror 3
.Sh HISTORY
The
.Fn psignal
function appeared in
.Bx 4.2 .
